I actually have used some of the HL books. He does have some really nifty tips. I found his system to be useful, but I just didn't stick with it. I suppose if you really really stuck with it, it may benefit you, but as a whole it almost required as much work using his system to memorize some lists as it would require to just memorize it. For example he teaches memorizing a grocery list by making a vivid story up in your head (a cow stepping on a chicken who was drunk while a farmer who was missing his socks was picking apples and oranges from a tree that fell over and knocked over a powerline which shocked a butcher who fell into a freezer right onto a big bucket of icecream, etc. to memorize a grocery list of milk, eggs, beer, socks, fruit, batteries, steaks, ice cream etc.). For me, it wasn't worth the trouble to use it for many things, but it wouldn't hurt to give it a shot!
Concepts are important, but I WOULD strive to be a walking refernce book. Many times a question is asked either in the clinic or pharmacy that you just don't have time to go look it up or you may just need to know it right then. A patient, doctor, fellow pharmacist, etc. often will want an answer right them and not an "I'll go look up the mechanism, dosage, interactions, ect."
Jason